The present invention relates to a jagged-edge killer circuit used for a three-dimensional display.
Hidden surfaces are removed when displaying three-dimensional image. Here, "hidden-surface" means a picture existing in a portion behind an object which has a short distance from a viewpoint in the depth direction within the three-dimensional image. In many case, the boundary generated between a hidden surface and a displayed surface as a result form the hidden surface removal, accompanies so-called jugged-edge or jaggy-edge.
The jagged-edge is wearsome for a viewer, therefore, it is desirable to adopt the jagged-edge killer with the hidden surface removal.
There is conventionally known a Z-buffer method as one of various jagged-edge killing methods, which has the merit of being capable of eliminating the jagged-edge in spite of the shape and output order of the surface to be displayed.
FIG. 1 shows a block diagram of the schematic structure of a conventional jagged-edge killer circuit used in the application of the jagged-edge killing by the Z buffer method.
In the figure, a Z-buffer 1 stores distance data in the depth direction corresponding to each pixel of a display frame buffer 3. The distance data of the depth direction, which is stored in the Z-buffer 1, is supplied to a renewal circuit 2 as data Z.sub.old.
The renewal circuit 2 receives data of the X and Y addresses of the pixels on the frame buffer 3, distance data Z.sub.new of the pixels in the depth direction, and a luminance I of the pixels, and compares the new distance data Z.sub.new of the pixels in the depth direction with the old distance data Z.sub.old of the pixels in the depth direction stored in the Z-buffer 1 when luminance or color data of the pixels is written in the frame buffer 3. Only when the new pixels have a distance shorter than the old pixels from the viewpoint in the depth direction, a writing signal S.sub.W renews the storage contents of the frame buffer 3 by the luminance I or color data corresponding to the new pixels, and the distance data Z.sub.new of the new pixels renews the storage contents of the Z-buffer 1.
A picture is reproduced from image data read out of the frame buffer 3 when the conventional circuit shown in FIG. 1 performs the jagged-edge killing. As the reproduced picture is quantized pixel by pixel at the killing, the luminance or color becomes discontinuous so as to generate jagged portions in a step-shape at an outline which has an ordinally continuous area.
Even though the jagged portions can be eliminated by means that the luminance or color can be displayed after adding a post-filtering, it is possible to obtain the reproduced picture only having a low resolution because of the reduction of the pixel numbers constructing one scene.